sound card interface – AB4UG Radioblog

KH6TY Sound card interface v0.3

Finally took the plunge and reworked the sound card interface. I wanted to make it a little more compact and try to put it into an enclosure.

v0.2 was built on another section of perfboard, but I messed it up and decided to build v0.3 on a piece of half sized Perma-Protoboard.

v0.3 currently half works. Getting sound through from the radio to the laptop seems to be working fine. Getting sound out from the laptop through to the radio doesn’t seem to be working that well though. Seems like there’s not enough voltage into the 2n4711 transistor to make the collector close the PTT line and make the radio transmit. Kind of wondering if I grabbed the wrong diodes that go before the transistor. I also seem to be getting some voltage loss in the 3.5mm connectors. Given how much they’ve been soldered and unsoldered, I should probably find new ones to replace them with.

Still some more hardware debugging to do on this latest iteration.

Update: Electronic devices are weird sometimes. You test them out and they don’t work. Leave them alone for a while, and then they start working. Not sure what it was I did in the sound card settings or in fldigi, but the interface seems to be working now (at least it triggers the PTT when I put fldigi into transmit mode). Now to see if I can actually make a QSO with it.

Update: Successfully made two contacts with the interface! First one was PSK31 with an op in Belgium on 20m and the second one was the W1AW/7 portable station in Idaho on 20m RTTY. Yay!

Instead of mounting it inside a tin, I mounted the board onto another piece of 1×4 lumber with some rubber shelf liner glued to it. It’s kind of neat to see it next to the laptop and imagine the currents flowing around in the circuit while I play.

Reworking the sound card interface

Now that the sound card interface finally seems to be working ok, I’m contemplating the merits of tearing it apart and playing with the component layout to make things more compact. It’s not exactly sprawling across the perfboard, but the component spacing can be reduced and there are a few places where I see that I can compress things a little more by changing the arrangement of some of the components. It’s certainly functional the way it is, but the mildly obssessive tweaker in me wants to keep optimizing the component placement for minimum size.

I should probably spend some more time playing with it before I take it apart.

Sound card interface success!

After some troubleshooting and help from Jason/NT7S and Robert/AK6L, the problem turned out to be the transformers. Apparently they were step up/step down transformers and not the 1:1 transformers I really needed. Ordered some new transformers from Mouser and put them on when they arrived.

Still ran into problems getting the radio to transmit a signal, but after a closer examination of the board, I discovered I had connected one of my ground wires to the wrong spot so the audio signal to the radio ended up going to ground instead of the radio. Duh.

Fixed that, connected everything up and was able to make my first digimode QSO using the new interface with KC8MGD up in Michigan. From where he was, I had a good signal and wasn’t splattering across the band, so that’s a good sign.

So excited that I got this working! Now I can work on either coming up with an enclosure for this prototype board or build v0.3 and try to make it more compact. I have two more transformers that I can use to build a second interface, which I might save for later once I’m finished messing with this prototype board. I think I’ll try to find some PS2/mini-DIN6 sockets so that I can plug/unplug cables to it and get a little more flexibility about what I can plug into the board.

Sound card interface troubleshooting

A little more troubleshooting on the sound card interface moved the problem from the radio settings (which I think I have set properly…blog post about my radio settings to follow) to the interface board.

If I use fldigi to transmit, nothing happens on the radio. PTT was being triggered, but I think that was flrig triggering the PTT over the serial port, and the radio would have been listening on the mic jack instead of the data port.

If I ground the collector lead of the transistor on the board to trigger PTT on the data port and then tell fldigi to transmit, then I hear transmitted sounds on the radio and there’s activity on the signal meter.

For some reason, the audio signal going out into the PTT part of the circuit isn’t enough to make the transistor switch and ground the collector pin.

I’ll have to go through that part of the circuit to make sure i have all the components right and wired up properly. Worst case scenario I’ll just wire in a button switch to manually ground the collector pin for manual PTT.

Messing with the sound card interface.

Still don’t know if any of my signals are making it out of the radio.

Using headphones, I can hear the sounds fldigi generates in response to the text I “transmit”, so I know there’s stuff coming out of the laptop. The radio goes into transmit mode, but there’s no activity on any of the meters so I can’t tell if anything is actually being transmitted.

Matthew/W2MDW suggested using pskreporter.info to see if I get spotted. After sending out a bunch of CQs, test messages and trying to respond to someone’s PSK31 signal, it didn’t appear that any of the listening stations heard my signal as far as I could see.

The data port pinout for the TS-480 has pin 2 as the audio signal ground, which is unconnected in the PS2 cable I’m using. I wonder if that could be messing up the audio that’s going into the radio.

Update: I can see there’s about 70 mVAC of signal going out of the interface into the radio, so at least there’s something getting to the radio. Not sure how much needs to be going into the data port to make the radio send stuff.